Conventionally, a mechanical joint for connecting a pair of rebars by inserting one of end portions of a rebar and one of end portions of another rebar in a sleeve is provided.
For example, a mechanical joint is provided in Patent Literature 1, in which one of end portions of a rebar and one of end portions of another rebar are inserted in a sleeve so as to abut against each other, and then the sleeve is pressed from the outer peripheral surface to bond the sleeve to the rebar.
In such mechanical joint, predetermined tensile strength has to be secured to hold the tensile force acting on the rebar. Such tensile strength is secured by a structure having a knot provided on the peripheral surface of the rebar or a structure providing interlocking of the knot with the inner peripheral surface of the sleeve.
As for the issue of securing the pull-out strength of the rebar, Patent Literature 2 proposes a rebar providing improved bonding strength to concrete. Epoxy powder coating is sprayed on a heated rebar to form a first anticorrosion film, and on the surface of the molten first anticorrosion film, a second anticorrosion film is formed with a powder coating which is a mixture of epoxy resin and curing agent. Innumerable number of protrusion formed by the second anticorrosion film enhances the bonding strength to concrete.
Patent Literature 3 proposes a method of attaching a metal sleeve to a concrete-reinforcing bar. In the method, a particle having higher hardness than both the concrete-reinforcing bar and the sleeve is disposed between the opposing surfaces of the sleeve and the bar. By the particle interlocking with the bar and the sleeve, the sleeve is bonded to the bar with sufficient force to hold the bar and the sleeve together.